Mehmet Gormez, Turkey’s senior cleric, led the prayers attended by hundreds of Istanbulites.

"There have been 10 acts by Daesh against Turkey so far. Our combat against any terrorist organization, especially the PKK and Daesh, will continue resolutely," Erdogan told reporters after the prayers.

Erdogan said the attack was being investigated in a multi-directional way. "The presence of Daesh in Turkey is not acceptable," he added.

Accompanied by Interior Minister Efkan Ala, Erdogan also visited the scene of the deadly suicide attack in Sultanahmet square.

A blast at the district on Tuesday morning killed 10 people – mostly German tourists – and wounded 15 others.

A Syrian suicide bomber carried out the attack, Erdogan said on Tuesday while Turkish Prime Minister Ahmet Davutoglu told reporters on Wednesday that the police identified the suicide bomber but did not supply a name.

Davutoglu said that the bomber had Daesh links, adding: "Police were not in pursuit of the bomber. He had come to Turkey as an ordinary refugee. However, after the attack, all his contacts were brought out.”

Within the scope of the ongoing investigations, police detained a total of seven suspects in connection with Tuesday's Istanbul suicide bomb attack, a Turkish minister said on Thursday.